Method and apparatus for actively manipulating aerodynamic surfaces

ABSTRACT

A method and apparatus is provided, including an actuator system that may be connected to a wing frame for controlling an active element. The actuator system may include sliding elements movable along an axis parallel to the span-wise axis of the wing. The sliding elements may be connected to fixed elements and a crank element, the crank element generally comprising a beam element and a pivot element. The beam element may be offset from the pivot element so that the crank element is rotatable about the pivot element with a negative stiffness under an external force that tends to pull the sliding elements away from the fixed elements.

TECHNICAL FIELD

This disclosure relates in general to the field of heavier-than-airaircraft, and more particularly to a method and apparatus for activelymanipulating aerodynamic surfaces.

DESCRIPTION OF THE PRIOR ART

Emerging and future generations of rotary-wing and tilt-rotor aircrafthave active elements on the blade or wing, such as trailing edge flapsand leading edge droops, which can provide a number of enhancements overpassive designs. For example, active elements can be used for vibrationreduction, noise reduction, and performance improvements. Actuatorsystems are needed to operate active elements, but actuator systems alsoadd weight and complexity to the aircraft. Accordingly, the design ofpowerful, light-weight actuator systems presents significant challengesto engineers and manufacturers.

BRIEF DESCRIPTION OF THE DRAWINGS

The features believed characteristic and novel of a method and apparatus(collectively, a system) for active manipulation of aerodynamic surfacesare set forth in the appended claims. However, the system, as well as apreferred mode of use, and further objectives and advantages thereof,will best be understood by reference to the following detaileddescription when read in conjunction with the accompanying drawings,wherein:

FIG. 1 is a perspective view of an example embodiment of a helicopteraccording to the present specification;

FIG. 2 is a partial top view of an example embodiment of a helicopterhaving an active blade element and actuator system according to thepresent specification;

FIG. 3 is a simple top-view schematic of an example embodiment of anactuator system according to the present specification having aspan-wise orientation and a parallel configuration of linear actuatorsin a rotor blade;

FIG. 4 is a simple side-view schematic of an example embodiment of anactuator system according to the present specification having aspan-wise orientation and a parallel configuration of linear actuatorsin a rotor blade;

FIG. 5 is a cut-away view of an example embodiment of a linear motoractuator according to the present specification;

FIG. 6 is a simple top-view schematic of another example embodiment ofan actuator system according to the present specification having aspan-wise orientation and a serial configuration of linear actuators ina rotor blade; and

FIG. 7 is a perspective view of another example embodiment of anactuator system according to the present specification having aspan-wise orientation and a parallel configuration of linear actuatorsin a rotor blade.

While the system and apparatus for active manipulation of aerodynamicforces is susceptible to various modifications and alternative forms,the novel features thereof are shown and described below throughspecific example embodiments. It should be understood, however, that thedescription herein of specific example embodiments is not intended tolimit the system or apparatus to the particular forms disclosed, but onthe contrary, the intention is to cover all modifications, equivalents,and alternatives falling within the spirit and scope of the appendedclaims.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Illustrative embodiments of the novel system are described below. In theinterest of clarity, not all features of such embodiments may bedescribed. It should be appreciated that in the development of any suchsystem, numerous implementation-specific decisions must be made toachieve specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it should be appreciated that such decisions might becomplex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

Reference may be made to the spatial relationships between variouscomponents and to the spatial orientation of various aspects ofcomponents as the system is depicted in the attached drawings. However,as should be recognized by those skilled in the art, the elements,members, components, etc. described herein may be positioned in anydesired orientation. Thus, the use of terms such as “above,” “below,”“upper,” “lower,” or other like terms to describe a spatial relationshipbetween various components or to describe the spatial orientation ofaspects of such components should be understood to describe a relativerelationship between the components or a spatial orientation of aspectsof such components, respectively, as the example embodiments describedherein may be oriented in any desired direction.

Referring to the appended drawings, FIG. 1 is a perspective view of anexample embodiment of a helicopter 10 according to the presentspecification. In general, helicopter 10 has a fuselage 12 and a mainrotor assembly 14, which includes main rotor blades 16 a-c and a mainrotor shaft 18. Helicopter 10 may also include a tail rotor assembly 20,which generally includes tail rotor blades 22 and a tail rotor shaft 24.Main rotor blades 16 a-c may rotate about a longitudinal axis 26 of mainrotor shaft 18.

Tail rotor blades may rotate about a longitudinal axis 28 of tail rotorshaft 24. Also illustrated in FIG. 1 are flaps 32 a-b and actuatorsystems 36 a-b on main rotor blades 16 a-b, respectively. Not visible inFIG. 1 are flap 32 c and actuator system 36 c on main rotor blade 16 c.

FIG. 2 is a partial top view of helicopter 10, including main rotorblade 16 a, connected to a hub 30 on main rotor shaft 18. In the exampleembodiment of helicopter 10, main rotor blade 16 a may includeadditional active elements that may be used to manipulate aerodynamicsurfaces, such as flap 32 a. Flap 32 a in the example embodiment ofhelicopter 10 is placed outboard along the trailing edge 34 a, but maybe placed in other positions according to particular design criteria.And while flap 32 a is illustrated and described herein as a distinctcomponent of main rotor blade 16 a, it may also be any movable orflexible portion of main rotor blade 16 a. An example embodiment ofactuator system 36 a is also depicted in the cut-away section FIG. 2,generally oriented parallel to a span-wise axis 17 a of main rotor blade16 a. During operation, main rotor blade 16 a may rotate about hub 30,while actuator system manipulates flap 32 a. The rotation causes anumber of reactive forces, including lift and centrifugal forces (CF).

FIG. 3 is a simple top-view schematic of actuator system 36 a in mainrotor blade 16 a. Actuator system 36 a may include linear actuators 38a-b. Each linear actuator 38 a-b typically includes a fixed orstationary element, such as stators 40 a-b, and a moving or slidingelement, such as sliders 42 a-b. Stators 40 a-b in the exampleembodiment are rigidly connected to the frame of main rotor blade 16 a,and they may be identical elements or may have distinct properties forcertain applications. Likewise, sliders 42 a-b may be identical or havedistinct properties for certain applications. Linear actuators 38 a-beach has an elongated shape with a lengthwise axis 39 a-b that isgenerally oriented parallel with span-wise axis 17 a of main rotor blade16 a. In the example embodiment of FIG. 3, linear actuators 38 a-b arealso generally oriented parallel to each other along the span of mainrotor blade 16 a. Such a span-wise orientation is generally preferableto other orientations as it generally provides larger space in the bladefor larger, more powerful motors with longer strokes, and better massplacement.

In actuator system 36 a, a crank 44 is connected to sliders 42 a-b.Crank 44 includes a beam element 46, a pivot element 48, and an armelement 50. Examples of pivot element 48 include a conventional bearingwith rolling elements, an elastomeric element, a sleeve bushing, or astructural flexure. Pivot element 48 may be positioned coincident withbeam element 46, or may be offset a distance L relative to beam element46, as shown in FIG. 3. By adjusting distance L, the large centrifugalforce acting on sliders 42 a-b may be used advantageously to create anegative stiffness spring effect, wherein the negative spring constant,k, is proportional to the centrifugal force CF, distance L, and angulardisplacement θ(−k=CF*L*sin(θ)/θ). The negative spring effect maycounteract aerodynamic forces and reduce actuator power requirements,thereby also potentially reducing the mass of actuator system 36 a. Armelement 50 may be rigidly attached to beam element 46, or beam element46 and arm element may 50 be fabricated as a single element.

FIG. 4 is a simple side-view schematic of actuator system 36 a. Stators40 a-b are preferably placed within the frame of main rotor blade 16 ain parallel. Connecting rod 52 connects actuator system 36 a to flap 32a through crank 44 (see FIG. 3) and sliders 42 a-b (see FIG. 3). Flap 32a may rotate about an axis 33 in response to force from connecting rod52. Alternate positions of flap 32 a as it rotates about axis 33 areillustrated in phantom as flaps 32 a-1 and 32 a-2.

FIG. 5 is a cut-away view of an example embodiment of a linear actuator60. In this embodiment, linear actuator 60 is an electromagnetic linearmotor having a fixed element, stator 62, having electric coils, and anelongated, high-power permanent magnetic slider 64. The slider 64 movesand converts electrical power to useful work. The motion, position, andretention of slider 64 are controlled with electromagnetic forcegenerated with the electric coils of stator 62. Such an actuator mayprovide benefits in certain applications where high bandwidth and largestroke with a small footprint are desirable. For example, anelectromagnetic motor such as linear actuator 60 may be advantageous ina helicopter rotor blade where vibrations and noise are counteractedwith relatively small flap deflections at high frequency, butperformance is enhanced with larger deflections at a lower frequency.

During rotation of main rotor blade 16 a, the centrifugal forces arecarried across beam element 46 and reacted by pivot 48, effectivelycanceling the tendency of sliders 42 a-b to sling outward because of thecentrifugal forces. Crank 44 is similar to a common bell crank, and asit rotates it converts the span-wise motion of sliders 42 a-b intochord-wise motion that may be used to manipulate an active element, suchas flap 32 a, which is connected to arm element 50 through a connectingrod 52 or similar linkage.

In operation, sliders 42 a-b are actuated such that each reciprocatesgenerally parallel to axis 17 a and slider 42 a moves opposite to slider42 b. Thus, as slider 42 a moves in the outboard direction of main rotorblade 16 a, slider 42 b moves inboard. And as slider 42 a moves outboardand slider 42 b moves inboard, crank 44 rotates about pivot element 48,causing arm element 50 to advance toward trailing edge 34 a of mainrotor blade 16 a. The movement of arm element 50 toward trailing edge 34a in turn causes connecting rod 52 to act on flap 32 a, which may rotateabout axis 33 to position 32 a-1.

Conversely, as slider 42 a moves inboard and slider 42 b moves outboard,crank 44 rotates in the opposite direction about pivot element 48,causing arm element 50 to retreat from trailing edge 34 a. The movementof arm element 50 away from trailing edge 34 b in turn causes connectingrod 52 to act on flap 32 a, which may rotate about axis 33 to anotherposition, such as 32 a-2.

FIG. 6 is a simple top-view schematic of another example embodiment ofan actuator system 70 in a main rotor blade 72 according to the presentspecification. Actuator system 70 may include linear actuators 74 a-b.Each linear actuator 74 a-b typically includes a fixed or stationaryelement, such as stators 76 a-b, and a moving element or slidingelement, such as sliders 78 a-b. Stators 76 a-b in the exampleembodiment are rigidly connected to the frame of main rotor blade 72,and they may be identical elements or may have distinct properties forcertain applications. Likewise, sliders 78 a-b may be identical or havedistinct properties for certain applications. Linear actuators 74 a-beach has an elongated shape with a lengthwise axis 75 a-b that isgenerally oriented parallel with span-wise axis 73 of main rotor blade72. In contrast to linear actuators 38 a-b in FIG. 3, linear actuators74 a-b are generally oriented in series along the span of main rotorblade 72.

In actuator system 70, a crank 80 is connected to sliders 78 a-b. Crank80 includes a beam element 82, a pivot element 84, and an arm element86. Extension elements 79 a-b may be used to connect sliders 78 a-b tobeam element 82. Examples of pivot element 84 include a conventionalbearing with rolling elements, an elastomeric element, a sleeve bushing,or a structural flexure. Pivot element 84 may be positioned coincidentwith beam element 82, or may be positioned a distance L relative to beamelement 82, as shown in FIG. 6. By adjusting distance L, the largecentrifugal force acting on sliders 78 a-b may be used advantageously tocreate a negative stiffness spring effect, wherein the negative springconstant, k, is proportional to the centrifugal force CF, distance L,and angular displacement θ(−k=CF*L*sin(θ)/θ). The negative spring effectmay counteract aerodynamic forces and reduce actuator powerrequirements, thereby also potentially reducing the mass of actuatorsystem 70. Arm element 86 may be rigidly attached to beam element 82, orbeam element 82 and arm element 86 may be fabricated as a singleelement.

During rotation of main rotor blade 72, the centrifugal forces arecarried across beam element 82 and reacted by pivot element 84,effectively canceling the tendency of sliders 78 a-b to sling outwardbecause of the centrifugal forces. Crank 80 is similar to a common bellcrank, and as it rotates it converts the span-wise motion of sliders 78a-b into chord-wise motion that may be used to manipulate an activeelement, such as flap 88, which is connected to arm element 86 through aconnecting rod 90 or similar linkage.

In operation, sliders 78 a-b are actuated such that each reciprocatesgenerally parallel to axis 73 and slider 78 a moves opposite to slider78 b. Thus, as slider 78 a moves in the outboard direction of main rotorblade 72, slider 78 b moves inboard. And as slider 78 a moves outboardand slider 78 b moves inboard, crank 80 rotates about pivot element 84,causing arm element 86 to advance toward trailing edge 92 of main rotorblade 72. The movement of arm element 86 toward trailing edge 92 in turncauses connecting rod 90 to act on flap 88, which may rotate about axis89.

Conversely, as slider 78 a moves inboard and slider 78 b moves outboard,crank 80 rotates in the opposite direction about pivot element 84,causing arm element 86 to retreat from trailing edge 92. The movement ofarm element 86 away from trailing edge 92 in turn causes connecting rod90 to act on flap 88, which may rotate about axis 89.

FIG. 7 is a perspective view of another example embodiment of anactuator system 100 in a main rotor blade 102 according to the presentspecification. Actuator system 100 may include linear actuators 104 a-b.Each linear actuator 104 a-b typically includes a fixed or stationaryelement and a moving or sliding element, such as sliders 106 a-b. Thefixed element may be rigidly connected to the frame of main rotor blade102, and they may be identical elements or may have distinct propertiesfor certain applications. Likewise, sliders 106 a-b may be identical orhave distinct properties for certain applications. Linear actuators 104a-b each has an elongated shape with a lengthwise axis that is generallyoriented parallel with a span-wise axis of main rotor blade 102. In theexample embodiment of FIG. 7, linear actuators 102 a-b are alsogenerally oriented parallel to each other along the span of main rotorblade 16 a. Such a span-wise orientation is generally preferable toother orientations as it generally provides larger space in the bladefor larger, more powerful motors with longer strokes, and better massplacement.

In actuator system 100, tension belts 108 a-b may be connected tosliders 106 a-b, respectively. Tension belts 108 a-b are routed aroundpivot elements 110 a-b, respectively, and then fastened to an activeelement 112, such as a flap.

In operation, sliders 106 a-b are actuated such that each reciprocatesgenerally parallel to the span-wise axis of main rotor blade 102 andslider 106 a moves opposite to slider 106 b. Thus, as slider 106 a movesin the outboard direction of main rotor blade 102, slider 106 b movesinboard. And as slider 106 a moves outboard and slider 106 b movesinboard, tension belt 108 b is pulled inboard about pivot element 110 b,causing active element 112 to rotate. Conversely, as slider 106 a movesinboard and slider 106 b moves outboard, tension belt 108 a is pulledinboard about pivot element 110 a, causing active element 112 to rotatein the opposite direction.

Alternatively or additionally, an actuator system may include hydraulic,piezoelectric, or electromechanical components. For example, a linearactuator may have a fixed element such as a hydraulic cylinder and amoving element such as a hydraulic ram.

The system and apparatus described herein provides significantadvantages, including: (1) reducing or eliminating the adverse effectsof centrifugal forces on linear actuators in a span-wise orientation;(2) more powerful motors; (3) longer stroke and greater bandwidth thanother systems; and (4) improved mass distribution characteristics.

Certain example embodiments have been shown in the drawings anddescribed above, but variations in these embodiments will be apparent tothose skilled in the art. The principles disclosed herein are readilyapplicable to a variety of aircraft, including many types of rotarywing, tilt-rotor, and fixed wing aircraft, as well as a variety of otheractive wing elements, including leading edge droops. The precedingdescription is for illustration purposes only, and the claims belowshould not be construed as limited to the specific embodiments shown anddescribed.

1. An apparatus, comprising: a first linear actuator having a firstfixed element and a first sliding element; a second linear actuatorhaving a second fixed element and a second sliding element; a beamelement connected on a first end to the first sliding element andconnected on a second end to the second sliding element; a pivot elementconnected to the beam element between the first sliding element and thesecond sliding element; and an arm element having a first end connectedto the beam element.
 2. The apparatus of claim 1, wherein the firstlinear actuator and the second linear actuator are electromagneticactuators.
 3. The apparatus of claim 1, wherein the first linearactuator is aligned parallel to the second linear actuator.
 4. Theapparatus of claim 1, wherein the first linear actuator is aligned inseries with the second linear actuator.
 5. The apparatus of claim 1,wherein the pivot element is offset from the beam element.
 6. Anaircraft, comprising: a fuselage; a wing having span-wise axis, a frameconnected to the fuselage, and an active element; and an actuator systemconnected to the frame and the active element, the actuator systemhaving sliding elements movable along an axis parallel to the span-wiseaxis of the wing and counterbalanced by each other through a pivotelement.
 7. The aircraft of claim 6, wherein the sliding elements aremovably disposed within fixed elements and connected to a crank element,the crank element comprising a beam element offset from the pivotelement so that the crank element is rotatable about the pivot elementwith a negative stiffness under an external force that tends to pull thesliding elements away from the fixed elements.
 8. An aircraft,comprising: a fuselage; a wing having span-wise axis, a frame connectedto the fuselage, and an active element; a first linear actuator having afirst stator element and a first sliding element; a second linearactuator having a second stator element and a second sliding element; abeam element connected on a first end to the first sliding element andconnected on a second end to the second sliding element; a pivot elementconnected to the beam element between the first sliding element and thesecond sliding element; and an arm element having a first end connectedto the beam element and a second end connected to the active element;wherein the first stator element and the second stator element arerigidly connected to the wing frame.
 9. The aircraft of claim 8, whereinthe first sliding element and the second sliding element are aligned tobe movable along an axis parallel to the span-wise axis of the wing. 10.The aircraft of claim 8, wherein the wing is rotatable about a hubconnected to the fuselage.
 11. The aircraft of claim 8, wherein the wingis rotatable about a hub connected to the fuselage and the first slidingelement and the second sliding element are aligned to be movable alongan axis parallel to the span-wise axis of the wing.
 12. The aircraft ofclaim 8, wherein the first linear actuator and the second linearactuator are electromagnetic motors.
 13. The apparatus of claim 8,wherein the first linear actuator is aligned parallel to the secondlinear actuator.
 14. The aircraft of claim 8, wherein the first linearactuator is aligned in series with the second linear actuator.
 15. Theaircraft of claim 8, wherein: the wing is rotatable about a hubconnected to the fuselage; the first sliding element and the secondsliding element are aligned to be movable along an axis parallel to thespan-wise axis of the wing; and the first linear actuator is alignedparallel to the second linear actuator.
 16. The aircraft of claim 8,wherein: the wing is rotatable about a hub connected to the fuselage;the first sliding element and the second sliding element are aligned tobe movable along an axis parallel to the span-wise axis of the wing; thefirst linear actuator is aligned parallel to the second linear actuator;and the pivot element is offset from the beam element.
 17. The aircraftof claim 8, wherein: the wing is rotatable about a hub connected to thefuselage; the first sliding element and the second sliding element arealigned to be movable along an axis parallel to the span-wise axis ofthe wing; and the first linear actuator is aligned in series with thesecond linear actuator.
 18. The aircraft of claim 8, wherein: the wingis rotatable about a hub connected to the fuselage; the first slidingelement and the second sliding element are aligned to be movable alongan axis parallel to the span-wise axis of the wing; the first linearactuator is aligned in series with the second linear actuator; and thepivot element is offset from the beam element.
 19. (canceled)